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What are We Doing at CERN, Anyway? Bryan Dahmes (University of Minnesota) ‏

What are We Doing at CERN, Anyway? Bryan Dahmes (University of Minnesota) ‏. What is Particle Physics?. Search for answers to very old questions What are we made of? What holds us together?. Ancient Greece: Fundamental Elements. What is Particle Physics?.

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What are We Doing at CERN, Anyway? Bryan Dahmes (University of Minnesota) ‏

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  1. What are We Doing at CERN, Anyway? Bryan Dahmes (University of Minnesota)‏

  2. What is Particle Physics? • Search for answers to very old questions • What are we made of? • What holds us together? Ancient Greece: Fundamental Elements

  3. What is Particle Physics? • Search for answers to very old questions • What are we made of? • What holds us together? “Atom”: Uncuttable, fundamental building block Early 20th century: Birth of the modern atom

  4. What is Particle Physics? • Search for answers to very old questions • What are we made of? • What holds us together? 1960s: Quarks

  5. What is Particle Physics? • Develop/Test the Standard Model • Describes (most of) the fundamental forces of Nature • Enumerates the particles that “see” these forces • Model built up over time based on theory and experimental results • The Standard Model does not answer all our questions

  6. What is Particle Physics? • What does the Standard Model get right? • Explains mass (Higgs mechanism) • Predicted particles (and their properties) before discovery • Unifies Electromagnetism and Weak Nuclear force • Repeatedly passes rigorous tests

  7. What is Particle Physics? • What still needs to be understood? • Higgs boson still missing • Gravity not part of SM • What about Dark Matter?

  8. Testing the Standard Model • How do we study the forces? • How can we study the fundamental particles? • Very few (known) stable particles • We must create them from scratch • How do you create “something” from “nothing”?

  9. Testing the Standard Model • How do we study the forces? • How can we study the fundamental particles? • Very few (known) stable particles • We must create them from scratch • How do you create “something” from “nothing”?

  10. Testing the Standard Model • Thanks to Einstein (Relativity) and Dirac (anti-matter) we can create “high energy” collisions Mass = Energy particle anti-particle New particles can be created from the collisions!

  11. Accelerators • Must speed up particles before colliding • Faster particles, more energy • Must steer particles into each other • Accelerators use Electromagnetism to do this

  12. Accelerators • Must speed up particles before colliding • Must steer particles into each other • Make particles travel in a circle • Accelerators use Electromagnetic Forceto do this proton v B out of page

  13. Accelerators proton • Must speed up particles before colliding • Must steer particles into each other • Make particles travel in a circle • Accelerators use Electromagnetic Forceto do this

  14. Accelerators proton • Must speed up particles before colliding • Must steer particles into each other • Make particles travel in a circle • Accelerators use Electromagnetic Forceto do this 1232 Dipole Magnets (15 m long) in the LHC tunnel (27 km cir.)

  15. The LHC at CERN

  16. The LHC at CERN • A few facts about the LHC: • 27 km ring 100 m underground • Accelerates protons to 7 TeV (10-9 J) • Proton energy nearly 7,500 mp • Proton speed: 99.99...% speed of light • Colder than outer space (1.9 K) • Proton travel in bunches around the ring • 1011 protons per bunch • 25 nsec (7.5 m) between bunches

  17. The LHC at CERN

  18. CMS Detector 12500 tonnes Diameter 15 m Length 21.6 m Magnetic Field 3.8 T Muon Chambers Hadronic Calorimeter (HCAL) EM Calorimeter (ECAL) Strip Tracker Pixel Tracker

  19. Event Display • Lots of things happen when protons collide...

  20. Detecting Particles B out of page B into page

  21. Understanding What Is Seen What is wrong with this picture?

  22. Understanding What Is Seen • “New Physics” may be discovered by looking for what isn't there ν

  23. A Few of My Experiences

  24. A Few of My Experiences

  25. Missing E/p at CMS

  26. So Many Events...

  27. Triggering • Inelastic collisions dominate event rate • Triggering on events • Level 1: 40 MHz to 100 kHz • Custom hardware • Fast, simple decisions • Further rejection (up to a factor of 1000) by High Level Trigger (HLT) • Massive commercial farm • Can store ~100 Hz • Throw away ~106 events for every event kept for further study New, Interesting events

  28. How Does All This Help Us? • The World Wide Web • SLAC: First US web page • Computing • Grid Computing • Homeland security • Detection of Nuclear Material • Medicine • MRI • Cancer treatment

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